The present invention relates to a method for manufacturing pressure sensing elements.
Pressure sensing elements of many different kinds are known. Because of their versatility and their suitability for a wide pressure range (for example, from 10 to 2000 bar), pressure sensing elements having a metal membrane and a resistive thin film arranged thereon have proven particularly suitable. A "resistive thin film" will be mentioned hereinafter; it is clear that this includes a plurality of individual films of various functions which together yield the resistive thin film. These pressure sensing elements possess a base element which has a measurement opening that is covered by the metal membrane (bottom of the measurement opening). When the measurement opening is acted upon by a pressure to be measured, the metal membrane and thus the resistive thin film applied onto the membrane experience a deflection which is detectable via suitable analysis means. It is known to manufacture pressure sensing elements of this kind by laborious individual production. In this, the base elements of the pressure sensing elements are produced from metal as turned parts; they are equipped with a blind opening; and then the resistive thin film is applied. Since this individual production is very laborious, manufacture in large quantities is not possible.
In order to allow more effective manufacture of the pressure sensing elements, it is known to process a larger number of pressure sensing elements, for example 50 to 70 units, using the so-called carrier technique. For this, the base elements, individually turned and polished and having the blind openings, are inserted into a carrier structure, for example a perforated panel, and are then together equipped with the resistive thin film. The disadvantage in this context, however, is that the film deposition process for applying the resistive thin film simultaneously contaminates the carrier element, so that the latter must be subjected to a laborious cleaning operation before being reused. A further disadvantage is that the carrier elements must be populated with the base elements and then, once processed, the pressure sensing elements must be removed from the carrier element. Another disadvantage is that the different processes, for example coating and photolithography, also require different carrier systems. The precision of the carrier directly affects the geometric accuracy of the individual elements.